Engineering Tissue with Blood Vessels
Lab-grown muscle gets nourishment

Results: Researchers in Robert Langer’s lab have coaxed skeletal-muscle tissue growing in a lab dish to develop its own network of blood vessels. When the researchers inserted the small piece of tissue into the abdominal muscle of a mouse, they found that 41 percent of the engineered tissue’s blood vessels connected with the mouse’s vascular system. After two weeks, twice as much of the engineered vascularized tissue survived as did control tissue without blood vessels.

Why It Matters: One of the biggest problems in tissue engineering is keeping cells alive after they’ve been implanted in the body. Researchers have had success implanting very thin layers of engineered tissue like skin, because they can use blood vessels from underlying tissue to deliver oxygen and nutrients and get rid of waste. Thicker engineered tissues like muscle, however, tend not to live long because they lack their own sets of vessels that deliver nourishment. Langer and his colleagues have taken an important step toward solving this problem: for the first time, they have gotten blood vessels to grow in a patch of engineered tissue before implanting it in the body. While the researchers focused on muscle tissue, a similar approach could work for other tissues that have a lot of blood vessels, such as liver or heart tissue.

Methods: Langer and his colleagues grew vascularized muscle tissue on a biodegradable polymer scaffold, which measured 25 square millimeters by one millimeter thick, by seeding it with three different types of cells: mouse muscle stem cells; human endothelial cells, which form blood vessels; and mouse fibroblasts, which give rise to connective tissue and smooth-muscle cells (the researchers hypothesized that these cells would stabilize the vessels). The researchers let the cells grow for several weeks. In one experiment, they removed part of a mouse’s abdominal muscle and replaced it with the tissue-covered scaffold. After two weeks, they removed the tissue and analyzed it. – By Lisa Scanlon

Source: Levenberg, S., et al. 2005. Engineered vascu- larized skeletal muscle tissue. Nature Biotechnology 23:879-884.